Transportation cards can be purchased at the airport, convenience stores, subway stations and tourist information centers. The card alone will cost 3,000 KRW
You can recharge your card (with cash only) at convenience stores or at ticket/recharge machines (near the gates) in subway stations. You can also recharge them directly at an ATM from your bank account.
The subway will cost between 1,400 - 1,500 KRW
Basic fee for blue/green buses: 1,200 KRW
Basic fee for red buses: 3,000 KRW
You can transfer for free to another bus (cannot be the same number bus as the one you got off from) or subway. You must tag the T-money card on the reader when getting off, otherwise you will be charged a full fee at the next stop.
You can transfer between buses and subway up to 4 times. The next leg of the trip must begin within 30 minutes after getting off the previous means of transportation. After 9 pm until 7 am the transfer time is one hour. You cannot transfer from subway to subway for free if you go through the gates and tag out.
You must have more than 250 KRW on your card in order to transfer.
If you mistakenly go to the wrong side of the subway platform, you have 5 minutes to go through the gates and to the correct side with no extra fee.